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Re: Objections to / uses of PSVI?

• To: xml-dev <xml-dev@l...>
• Subject: Re: Objections to / uses of PSVI?
• From: Ronald Bourret <rpbourret@r...>
• Date: Thu, 16 May 2002 02:16:53 -0700
• References: <YVMG43A0KF07VXTKJUVC9MJ86UTC0.3ce25d14@MChamp>

Mike Champion wrote:
> As I understand it, "PSVIs" can be generated from DTDs or W3C Schemas.

Like a DOM tree, they can be generated from anything -- well-formed XML
documents, databases, your horoscope -- as long as you're willing to
write the code.

> The beastie existed in XML 1.0, but the schema people gave it a name,
> and introduced new thingies that magically pop into existence, such as
> the type information.  The DOM's experience in dealing with the
> unimagineable complexity introduced by generated values that magically
> pop into existence should be a warning to others...

From looking at the list of PSVI information items, it adds a single new
thing that "magically pops into existence" -- element default values.
Everything else (type information, validity information) no more
magically pops into existence than a node name does.

While I think there is a valid complaint about the sheer complexity of
the type information in the PSVI and the difficulty of both designing
and implementing an interface to it, I'm afraid the above argument falls
into the category of FUD.

> [Hmm, I think it's time to re-read that book yet again ... the very
> chapter titles make it sound like Brooks is talking about XML
> rather than System 360: "The Tar Pit" ... "The Second System
> Effect" ... "Why Did the Tower of Babel Fall" .... "Ten Pounds in a
> Five-Pound Sack" ... "Plan to Throw One Away" ... "Hatching a
> Catastrophe."]

This should be mandatory reading for all designers (including WG
members), especially the chapter on planning to throw one away.

-- Ron

• References:
  • Re: Objections to / uses of PSVI?
    • From: Mike Champion <mc@x...>

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